1. Field of the Invention
The present invention relates to a manufacturing technique for selectively etching a minute region. In particular, the present invention relates to a manufacturing technique of an integrated circuit substrate, in which a minute opening is formed, used for display devices such as flat panel displays.
2. Description of the Related Art
Thin film transistors (also referred to as “TFTs”) and electronic circuits having TFTs are manufactured by the steps of stacking various thin films such as a semiconductor film, an insulating film, and a conductive film over a substrate, and appropriately forming the films into predetermined patterns by a photolithography technique. A photolithography technique is a technique of transferring a circuit pattern or the like, which is called a photomask and is formed from a non-light-transmitting material on a transparent flat plate, onto a substrate utilizing light-exposure, and is widely used in the process of manufacturing semiconductor integrated circuits and the like.
A conventional manufacturing process using a photolithography technique involves a number of steps such as light-exposure, development, baking, and peeling, for handling a mask pattern which is formed from a photosensitive organic resin material called a photoresist. Therefore, the more the number of photolithography steps is increased, the more the manufacturing cost is inevitably increased. In order to overcome such drawbacks, a manufacturing process of TFTs with a reduced number of photolithography steps has been studied (refer to Reference 1: Japanese Published Patent Application No. 2000-133636). In Reference 1, a resist mask formed by photolithography steps which is used once is subjected to cubical expansion by swelling, so that the mask can be used again as a resist mask with a different shape.